College - Author 1

College of Engineering

Department - Author 1

Biomedical Engineering Department

Degree Name - Author 1

BS in Biomedical Engineering

College - Author 2

College of Engineering

Department - Author 2

Biomedical Engineering Department

Degree - Author 2

BS in Biomedical Engineering

College - Author 3

College of Engineering

Department - Author 3

Biomedical Engineering Department

Degree - Author 3

BS in Biomedical Engineering

Date

3-2020

Primary Advisor

Michael Whitt, College of Engineering, Biomedical Engineering Department

Additional Advisors

Christopher Heylman, College of Engineering, Biomedical Engineering Department

Abstract/Summary

The left atrial appendage senior design team aims to assist in closing off the left atrial appendage that is susceptible to coagulation due to non-valvular atrial fibrillation. Coagulation in the left atrial appendage (LAA) can be life threatening as it can lead to a stroke. Dr. Chris Porterfield performs a procedure that uses the Boston Scientific Watchman to close the appendage. He finds that sizing the Watchman properly is difficult with limited visuals from live CT scans. He proposed converting the CT scans into a 3D printed model of the left atrial appendage and left atrium so he can visually measure the opening and predict the trajectory angle of the Watchman device into the left atrial appendage. He currently has a base algorithm and procedure to convert and modify the CT scan into a .stl file, which can then be printed with standard PLA material using a 3D printer on Cal Poly’s campus. The project is limited to the printers and their material capabilities on Cal Poly’s campus. There are currently many programs that convert CT scans to printable files and this project aims to evaluate each to conclude which produces the most accurate 3D model. The procedure to create the model must also be quick to perform, repeatable and reproducible as well as easy to follow. After researching the various programs, we concluded that 3D Slicer allows us to print anatomically accurate models of the left atrium and LAA. Using this software, the user uploads CT scans obtained from the radiologist as a DICOM file. Once uploaded, the user will proceed to setting the threshold parameter to the designated values. The user will then scroll through the CT scan to identify the left atrium and LAA in one of the views. After locating the anatomies, the user will use the scissors tool to extrude out any unnecessary anatomy. Once isolated, the model will need to be hollowed out and set to the defined parameters. After a final cut is made to open the model for internal viewing, is it saved as a .stl file and sent to a 3D printing software such as Cura. From this point on, the user will refer to the printer’s manual for the printing procedure while using the parameters we listed as a guide. After the print is concluded, the user will be able to measure the opening of the LAA and determine which entry angle is most optimal. The key customer requirements we aimed to achieve were ease of use, time, production cost, shape/accuracy, repeatability and reproducibility. For ease of use, we had users go through our MPI, Training Guide and Operations Manual and had them rate between 1-10 on how clear and concise our directions were. We scaled the range so that 1 meant that our procedure was clear and concise enough to replicate while 10 meant it was near impossible to follow. We aimed to achieve an average score of less than 3. For time, we were given a timeframe of 24 hour to fully slice and print the model. Since this procedure is not officially ICD-9 billable yet, the cost of production must remain below $50 per print. Based on the sizing chart provided by Boston Scientific for the various sizes of the Watchman device, we decided that the shape/accuracy must be less than 10% variation from the CT scan, while the repeatability and reproducibility must have no statistical difference in variation from the ANOVA. After running ANOVA on the data obtained from measuring the 9 testing prints, the results showed that our slicing/printing procedure and the measurements taken for testing were adequate enough to prove the functionality of all our protocols. The results of ANOVA showed that there were no significant differences in our data except for depth reproducibility which means that our customer requirements of reproducibility and repeatability were almost met. For the ease of use requirement, Dr. Porterfield and his clinical specialist, Sarah Griess, went through our Manufacturing Process Instructions, 2 Training Guide, and Operations Manual and performed the feedback survey we provided. Based on those results, we concluded that our protocols are functional and easy to follow which is essential to producing an accurate model. To prove model accuracy, we had Dr. Porterfield size the Watchman device as he currently does and confirmed that our printed models were accurate.

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